/*
 * Binary Counter
 * by Steven Lehrburger
 * 27 May 2008
 *
 * Combines the Loop and Button examples to create an array of lights that counts
 * the number of times the switch has been pressed in binary.
 */

int pins[] = { 2, 3, 4, 5, 6, 7 };            // an array of pin numbers
int num_pins = 6;                             // the number of pins (i.e. the length of the array)
int count;
int inputPin = 8;                             // choose the input pin (for a pushbutton)
int val = 0;                                  // variable for reading the pin status

void setup()
{
  pinMode(inputPin, INPUT);                   // declare pushbutton as input
  
  count = 0;                                  // start the count at zero

  for (int i = 0; i < num_pins; i++)          // declare each pin as output
    pinMode(pins[i], OUTPUT);
}

void loop()
{
  val = digitalRead(inputPin);                // get the button state
  
  if (val == HIGH) {                          // if the button was depressed
    count++;                                  // increment the counter
    displayNumber(count);                     // illuminate the appropriate LEDs
  //  turnOnAll();
    delay(200);                               // so holding it down doesnt count too fast
  }
}

void turnOnAll()                              // was used for debugging - just turns on all the lights
{
  for (int i = num_pins; i >= 0; i--) {
    digitalWrite(pins[i], HIGH);
  }  
}

void displayNumber(int number)                // illuminates the LEDs for the passed number
{
  int remaining = number;                   
  for (int i = num_pins; i >= 0; i--) {       // starting with the last pin (that has the largest value) and going down
    if ((remaining - exponent(2, i)) >= 0) {  // if that pin is larger than the remaining value
      digitalWrite(pins[i], HIGH);            // illuminate that pin
      remaining -= exponent(2, i);            // and subtract the value from the number and keep going
    }
    else {
      digitalWrite(pins[i], LOW);             // otherwise, the pin is off
    }  
  }
}

int exponent(int base, int power)             // simply calculates an exponent - perhaps there is a library with this
{                                             // but it was faster to rewrite it
  int result = 1; 
  for (int i = 0; i < power; i++) {
    result *= base; 
  }
  return(result);
}